Method of forming high pressure tanks



May 21;, 1935. B. BART METHOD OF FORMING HIGH PRESSURE TANKS Filed Feb. 2, 1931 mMW////////////%//// INVENTOR BLASIUS BART n Patented May 21, 1935 UNITED STATES PATENT oFFIcE z,oo1,99s

METHOD oF FomvnNG man PRESSURE TANKS f Blasius Bart, East Grange, N.v J. Application February 2, 1931, Serial No. 512,990

2 Claims.

Seamless tanks, filed February 2, 1931, Serial l In the manufacture of receptacles, tanks', con' lo' tainers and the like designed to withstand high internal or external pressures on the walls thereof, it has been necessary heretofore to make the walls with `an amount of material necessary to give the requisite tensile strength and rigidity to maintain the configuration of the article under the distorting strains to -which they are intended to be subjected. This necessity for struc-- tural strength has required the use of a material amount of metal in forming the walls and this in turn has made them heavy in weight and of course expensive to manufacture.

. The primary object of this invention, as is the object in theabove'identied copending applications, is to-provide a high pressure tank or other hollow structure having a high degree'of tensile strength and which at the same time will be light in weight and which can be manufactured economically both in labor Ncost and in the amount of material used.

'The invention features primarily the formation ona suitable mold or pattern of alternate layers of a shell comprising electrolytically deposited metals formed and assembled in a novel Way tov give to- -the resulting shell a tensile strength greater than would be obtained by following conventional methods.

Heretofore in forming hollow articles by electrolytic deposition on molds and patterns, it has been a usual practice to form the first deposit or layer on a mold covered with some form of deposit receiving material such as graphite, or to form this initial deposit'on a metal mold of some readily fusible or( meltable .material Such sur` faces are rough, or perhaps more accurately defined, are porous or coarse grained and react on the deposited layer to give to it a rough texture necessitating the formation of a layer of material thickness in order to give therequisite strength required of the shell forming the completed ar- 50 ticle." Continuing the deposition following known practices, there results a`development of positive granulation in the succeeding layers with rel lack of cohesion between the particles 'f and a resulting weakness in tensile strength.

65 'The present invention features the formation of (Cl. 20d-6) the electrolytic deposition on surfaces which are smooth, even high polished, which are homogeneous, non-porous and otherwise capable of forming a fine grained, adhesive layer of high tensile strength in distinction from the layers of metal mold and other surfaces. Examples of faces which act satisfactorily when following the method herein disclosed are polished sheet minum, highly polished electrolytically deposited copper and nickel, particularly copper.

low tensile strength formed heretofore when the same metals have been deposited on the usual alu- In forming articles by' electrolytic .deposition it has been found that the presence of cracks,

joints, re-entrant angles and other recesses andV depressions in the surface receiving the deposition has the effect of weakening the deposited layer.

Accordingly, the present disclosure features the providing of deposit receiving surfaces which are the dis-

closure, aan object of the invention is to provide a neat appearing tank designed to con re extinguishing and other chemical fluids der high pressure; which will be resistant to chemical reactions with such uids, which be light in weight and which will possess tain any will certain economical factors in design and construction contributing to low manufacturing costs.

Various other objects and advantages of invention will be in part obvious from a considthe eration of the method features of the disclosure and from an inspection of the accompanying drawing and in part will be more fully set forth in the following particularde'scription of one parts hereinafter set forth and claimed.

In the accompanying drawing: Fig. 1 is a View in axial cross sectioniof atank` in process of manufacture, before the form or mold is removed, illustratinga preferred emb ment of the invention and parts broken awa Odiyto reduce the size, but it is to be understood that the layers are' shown in enlarged cross sectional dimensions;

Fig.2 is an enlarged cross sectional view taken oir the line`2-2 of Fig. 1; and greatly enlarged to the Fig. 3 is a view similar to that shown in Fig. 2 illustrating on the same scale the two innermost deposited layers in a stage of the forming of the shell'shown in Fig. 2, prior to the addition of the third layer shown in this figure.

Referring particularly to the showing in Fig. 1, there is disclosed an internal mold vor pattern consisting primarily of two open end cylindrical shells I0 and II disposed with their open ends in abutting relation to form a joint I2. 'I'hese shells are formed of sheet aluminum, preferably spun to shape to avoid the presence of joints or other breaks in the exposed surfaces. For the purpose ofinsuring the maintaining of the abutting ends in fixed abutting relation, it is herein suggested that the ends'of the shells be telescoped over a rugged rigid aluminum reinforcing ring I3 designed to have a snug fit in the open ends ofthe shells. The shell II is pro'- vided at its opposite end with a dome-like, substantially semi-spherical head I4 provided at its crown with a bolt opening I5'. At the opposite end of the shell I IA is fixed a preformed threaded brass collar I6 designed to form part of the n- .ished fire extinguishing" devices. The collar is provided with a shouldered portion I'l merging at its inner end into a pointed edge I8 designed to form on both the inner and outer surfaces a smooth joint with the adjacent portion I9 of the. shell II which telescopes the same. -In assembling the, mold, a bolt 20 is inserted into the opening I5 with the headed end 2I of the bolt fitting within a countersunk recess I5 in the portion of the dome head I4 which contains the opening I5. The shank 22 of. the bolt extends into the interior of the shell and projects for a shortlxdistance axially thereof. The bolt is in threaded engagement with a tie rod 23, the opposite end of which extends through the opening in the collar IG and is provided exteriorly thereof with a nut 24. The parts are so designed that tightening up on the nut 24 will cause the shells I0 and\II to b drawn together by axially directed pressure. referably the nut 24 is formed of insulating material where it is designed to stop 01T depositions on the outer end of the collar I6.

It is a feature of the disclosure that'the portion of the mold which is designed to receive the metal deposited by electrolytic deposition as hereinafter described be continuous and smooth. To'attain this, it is necessary that all cracks, joints and other recesses be filled and smoothed to provide a continuity of surface across the same. For this purpose, solder, preferably a tin solder filler 25 is inserted in the joint I2 before, but preferably after the -nickel layer 29 hereinafter described hasbeen deposited and a similarly solder filler 26 is positioned about the periphery of the bolt head 2l toy fill in the recess between the outer periphery of the head and the adjacent portion of the dome head I4. Preferablyvthe solder 2B is linserted in place after the nickel layer 29 is in place. Similarly, fill- .ing solder 21 is positioned to ll out any depressionsfwhich may be formed between the collar I 6 and the portion I9 of th shell II. When the parts have thus been assembled, the exposed surface designed to receive the outermost deposimore accurately defined, a cloud-like mist of copper 28. The layer may be deposited by chemical precipitation or by electrolytic precipitation. ThisI copper layer, if used at all, is so thin that it offers no resistance to the aluminum dissolving action hereinafter described and has no effect upon the requisite Ismoothness of the polished aluminum mold.

'I'he mold, either with or without this film of copper, is positioned in an electrolytic bath containing nickel and a layer 29 of nickel is formed thereon. In the practicing of this method, certain refinements are observed in that preferably the temperature is maintained between F. and F. It hasbeen found that where the temperature was materially below 110 F., the deposit tended to become brittle, and at temperatures materially greaterthan 140 F., the resulting layer tended to lack the requisite tensile strength.

'I'his deposition of nickel is continued until there is a layer formed of about fifteen thousandths of an inch and this is best attained with a current density of about twenty-five to thirty amperes per square foot While the nickel layer thus formed is characterized by a much smoother outer face than would be the case if it were formed on the relatively rough mold surfaces heretofore known in this art, it is still true that the outer surface is not strictly smooth and under the microscope would show irregularities, indentations, ridges and the like, shown in an exaggerated form by the line 30 in Figs. 2 and 3.

'I'he recesses are filled with solder ifv not already filled, as above suggested, and the nickel and solder surface is then polished.

For the purpose of filling up these imperfections, pores and other minute recesses exposed in the nickel layer, the assemblage is then inserted in an electrolytic tank containing copper and a, copper layer 3| is deposited thereon as shown in Fig. 3. In general, the outer surface 32 of the copper layer will conform at least substantially to the configuration of the outer face 30 of the nickel layer. This electric deposition of copper takes place under substantially the same conditions as is indicated above in the deposition of nickel except that the current strength is usually somewhat higherv being about 30 to 40 amperes per square foot.

The assemblage is then removed from -the cop- -per bath and the copper surface is ground down to provide a smooth surface indicated by the line af-b in Fig. 3. Preferably, the grinding is continued substantially until the high points 33 of the nickel begin to show or are about to show. This outer surface 34 of the copper is polished to provide the smooth, continuous, homogeneous and non-porous surface corresponding to the surface of the polished aluminum mold which received the rst deposit 28 or 29 as the case may be.

'Ihe assemblage with its polished exposed copper surface is again positioned in the electrol'y tic tank containing nickel, and a third or in the instant case, a. fourth layer 34 is formed on the smooth polished outer face of the copper layer 3 I. It is noted from the construction shown in Fig. 3 that there is formed in effect two relatively thick layers 29 and 34 of nickel anda thin filling layer 3l of copper positioned between the two nickel layers. 'I'here is therefore formed in effect a shell, composed largely and primarily of alternate layers of electrolytically deposited nickel with just enough copper in an intermediate layer to cover imperfections and close up pores which may be formed in the inner nickel deposition. In the final analysis, there is formed practically a. nickel shell formed of extremely thin laminations of the order of about twenty-five thousandths of an inch, with the laminations sepa.- rated by even a thinner film copper electrolytically deposited and which copper is used primarily for the purpose of providing smooth deposit receiving surfaces for the succeeding nickel layer rather than to add structural strength to the nickel.

For ordinary purposes, the tank with two layers of nickel and an intermediate layer of copper is suiiicient to give the requisite rigidity to tanks designed to withstand pressures of 500 to 700 pounds, but it is obviously within the scope of the disclosure to position a succeeding layer of copper on the nickel layer 34, to grind down this next copper layer as suggested for the layer 3l and to then deposit a succeeding layer of nickel on the copper layer, and to continue this alternate deposition of copper and nickel until any desired or requisite thickness of shell has been obtained.

When the desired article has been completely formed, preferably with a nickel or chromium outer surface to give it a pleasing, polished appearance, the aluminum mold, together with the reinforcing ring, is dissolved out of the finished tank. Preferably the mold when formed of aluminum is dissolved out of the completed article with solution of sodium hydroxide, but it is within the scope of the disclosure to use other suitable solvents, such for instance as hydrochloric acid. Dissolving the sheet aluminum form from the mold as thus described, carried with it any thin film of copper such as the lm 28 hereinbefore described so that there remains a nickel lined receptacle. The nut 24 is unscrewed either before or after the mold has been dissolved and the connecting rod 23 and bolt 20 withdrawn through the opening in the collar I6. The finished tank contains the collar I6 which is electrolytically soldered in place by means of the laminated shell thus described.

Pressure tanks as thus formed are capable of withstanding high pressures and in the illustrated instance a tank weighing seven and onehalf pounds andl having a capacity of twelve quarts was subjected to an internal pressure of one thousand pounds, without becoming distorted or leaky. 'I'he tank thus formed under test showed greater tensile strength than was the case where the article was formed on a fusible metal form following conventional practices and where no particular care was taken to polish the surface of the mold or to p'olish the surface of the copper deposits as they were formed on the nickel layers. While the invention has been described, particularly with reference to the combination of nickel and copper, these metals have been selected primarily due to the high tensile strength of nickel and to the ease with which the copper could be used as a filler and due to the ease with which it could be highly polished, but it is obvious that other equivalent metals might be utilized and as one illustration, it is suggested that cobalt and cadmium be substituted for the nickel and copper. Sheet aluminum has been selected as the material from which the mold was formed due to the ease with which it could be subsequently dissolved without effecting the electrolytically deposited metals and due to the fact that it could be easily provided with a high lustre or polish. It is obvious, however, that other homogeneous, ne grained and non-porous metals might be used, as one illustration, it is suggested that zinc may be substituted for the aluminum mold or frame herein disclosed.

I claim:

1. In the art of forming hollow metal articles lined with nickel by electrolytic deposition, the method which consists in assembling parts of a mold having smooth deposit receiving, exposed surfaces and with the parts in abutting rela,-

tion forming joints, depositing a thin layer of copper on the mold, subjecting the mold thus prepared to the action of an electrolytic bath containing nickel, at a temperature not materially greater than 140 F. and not materially lower than 110 F. with a current density of approximately 25-30 amperes per square foot and until about twenty-five thousandths of an inch of nickel has been deposited to form the lining of the completed article as a one-piece layer of nickel on said copper coated smooth receiving surface of the mold, soldering any exposed joints between the parts of the mold to provide with the initial nickel layer a continuous, smooth, unbroken surface to receive the succeeding deposition and electrolytically depositing an additional layer of metal on the nickel lining and subjecting the mold with its thin layer of copper to the dissolving action of a reagent incapable of dissolving nickel or copper.

2. In the art of forming hollow metal articles lined with nickel by electrolytic deposition, the method which consists in assembling parts of a mold having smooth deposit receiving, exposed surfaces'and with the parts in abutting relation forming joints, depositing a thin layer of copper on the mold, subjecting the mold thus prepared to the action of an electrolytic bath containing nickel to form the lining of the completed article as a one-piece layer of nickel on said smooth receiving surface of the mold, soldering any exposed joints between the parts of the mold tb provide with the initial copper and nickel layers a continuous, smooth, unbroken-surface to receiveethe succeeding deposition, electrolytically depositing an additional layer of metal on the nickel lining and dissolving the mold with its thin layer of copper out of the resulting nickel lined article. BLASIUS BART. 

